Process for removal of pollutants from waste gas emissons
Chlorine is injected in a gaseous liquid or solution form into a hot (greater than 100.degree. C.) gas stream for the purpose of oxidizing objectionable components in the gas stream, such as, but not restricted to, SO.sub.2 and NO.sub.x, when the oxidized form of the gases is more readily removed from the gas stream. After sufficient reaction time, the gas stream mixture passes through water scubbers for the further removal of the components from the gas stream. Acidic and basic compounds of the gas stream and halogens, including excess chlorine, are also removed in the scrubbers. The pollutants remain as the corresponding oxidized acids or salts in the process effluent solution.
FIG. 1 illustrates a flow sheet depicting a laboratory equipment train which has been operated to establish the efficacy of the process.
FIG. 2 illustrates a physical embodiment of the process for use as a flue gas cleanup system as would be used by an electrical utility or similar large scale user.
FIG. 3 illustrates in graphic form the reaction of NO with Cl.sub.2 over a specified temperature range both with and without the presence of water vapour.
FIG. 4 illustrates in graphic form the reaction of NO with Cl.sub.2 (at lower concentrations) over a specified temperature range with and without the presence of water vapour.
FIG. 5 illustrates in graphic form the reaction of NO with Cl.sub.2 in the presence of water vapour at 409.degree. C.
FIG. 6 illustrates in graphic form the reaction of NO with Cl.sub.2 in the presence of water vapour at 450.degree. C.
FIG. 7 illustrates in graphic form the reaction of SO.sub.2 with Cl.sub.2 in the presence of water vapour at 200.degree. C.
FIGS. 8 and 9 illustrate the reaction of FIG. 7 at temperatures of 400.degree. C. and 450.degree. C.
FIG. 10 illustrates in graphic form the effect of SO.sub.2 on NO removal by Cl.sub.2 in the presence of water vapour at 400.degree. C.
FIG. 11 illustrates in graphic form the effect of NO on SO.sub.2 removal by Cl.sub.2 in the presence of water vapour at 400.degree. C.
FIG. 12 illustrates in graphic form the effect of scrubbing with water after reacting NO with Cl.sub.2 in the presence of water vapour at 450.degree. C.
FIG. 13 illustrates in graphic form the effect of scrubbing with water after reacting SO.sub.2 with Cl.sub.2 in the presence of water vapour at 450.degree. C.
FIG. 14 illustrates in graphic form the effect of SO.sub.2 on NO removal by Cl.sub.2 in the presence of water vapour at 200.degree. C. followed by water scrubbing.
FIG. 15 illustrates in graphic form the effect of NO on SO.sub.2 removal by Cl.sub.2 in the presence of water vapour at 200.degree. C. followed by water scrubbing.
FIG. 16 illustrates in graphic form the effect of NO on SO.sub.2 removal by Cl.sub.2 at 450.degree. C. followed by water scrubbing.
DETAILED DESCRIPTION OF THE INVENTIONThe process for gas stream cleanup is designed to oxidize objectionable components of the gas and in doing so render them non-volatile or much more readily absorbed. This oxidation will occur either in the gas phase or in solution in the scrubbers. The process can be used to simultaneously remove or reduce the amount present of the following; SO.sub.2, NO.sub.x, H.sub.2 S, ammonia, mercury and other metallic vapours, although it will be evident to anyone skilled in the art that this is by no means a complete list of readily oxidizable compounds which may be removed from gas streams. Because of the pH or chemical composition of the scrubber solutions used in the process, the process will remove almost any acidic or basic compounds as well as halogens from the gas stream.
Gas streams of temperatures of at least 100.degree. C. may be treated according to the invention. Excellent results are obtained with gas streams having temperatures between 100.degree. C. to 650.degree. C. Chlorine/sulphur dioxide ratios of at least 1.0 are preferred.
The process may be preceded by a dry electrostatic precipitator or baghouse of standard design operated at the gas stream temperature. The function of the precipitator or baghouse, if used, is the removal of particulate matter from the gas stream, as would be needed in the use of this process as a flue gas cleanup system. A high energy wet scrubber may be used as the optional third stage of the process as an alternative particulate removal device, if desired. Particle collection may be omitted as desired, and is not the subject of the invention.
EXAMPLESA large number of tests have been conducted on laboratory equipment as depicted schematically in FIG. 1 to demonstrate and establish the viability, performance and parameters of the applicant's process. The results of a large number of these tests are illustrated in the graphs and tables which follow.
Data was obtained using the following equipment:
Beckman Model 951 NO/NO.sub.x analyzer
Thermo Electron TECO Series 40 SO.sub.2 analyzer
Cl.sup.- Electrode--Orion combination electrode Model 96-17B
Orion Model 901 Ionanalyzer
Gas heating was by means of a tube furnace, controlled by a Variac transformer and an electronic temperature controller.
Generally speaking, the graphs fall into two groups: (a) gas phase reactions (Graphs 1-9) (FIGS. 3-11); and (b) gas phase reactions followed by water scrubbing (Graphs 10-14) (FIGS. 12-16). The scrubber solution became acidic in use due to the reaction products. The scrubbing effectiveness continued to be adequate to a pH of less than 1.
Graph 1 (FIG. 3)The reaction of 9,500 ppm NO with 19,000 ppm Cl.sub.2, both with and without water vapour, was examined over the range 50.degree.-450.degree. C. Over 200.degree. C., the water vapour definitely enhanced the NO/Cl.sub.2 reaction to 30 percent removal. (From previous work, it is known that at temperatures above those examined here, much larger reductions in NO levels are achieved.)
Graph 2 (FIG. 4)The reaction of 6,000 ppm NO with 12,000 ppm Cl.sub.2, both with and without water vapour, was examined over the range 50.degree.-450.degree. C. Over 200.degree. C., the water vapour definitely enhances the NO/Cl.sub.2 reaction to 30 percent removal.
Graph 3 (FIG. 5)The reaction of 9,000 ppm, 2,800 ppm and 1,600 ppm NO with varying Cl.sub.2 to NO mole ratio was examined in the presence of water vapour at 400.degree. C.
Graph 4 (FIG. 6)The reaction of 9.000 ppm and 2,800 ppm NO with varying mole ratios of Cl.sub.2 to NO was examined in the presence of water vapour at 450.degree. C.
Graph 5 (FIG. 7)The effect of water vapour on the removal of SO.sub.2 in the gas phase with varying mole ratios of Cl.sub.2 to SO.sub.2 was examined at 200.degree. C. A definite enhancement of SO.sub.2 removal was seen. The upper trace shows the effect of a very small amount of condensation on the inside of the inlet tube to the empty scrubber, clearly showing the extreme reactivity of SO.sub.2 and Cl.sub.2 in solution. The condensation appears to be enhanced by the gas reaction products, which condense on the cool glass, and being highly hygoscopic remove water vapour from the gas steam. Avoiding this effect required washing and drying the empty scrubber tube between readings of gas containing water vapour, taking readings as quickly as possible. The dry reaction was immediately rechecked to see if the observed condensation had effected the reading from a similar check immediately before the water vapour was added.
Graphs 6, 7 (FIGS. 8 and 9)Similarly, the effect of water vapour according to Graph 5 above was examined at 400.degree. C. and 450.degree. C.
Graph 8 (FIG. 10)The effect of SO.sub.2 on the removal of 12,000 ppm NO by varying mole ratios of Cl.sub.2 to SO.sub.2 in the presence of water vapour at 400.degree. C. was examined. Little effect was seen, and the results are within the range of experimental error of zero effect.
Graph 9 (FIG. 11)Complementing Graph 8, the effect of NO on the removal of 7,000 ppm SO.sub.2 from the gas phase at 400.degree. C. in the presence of water vapour was examined. A significant enhancement of the removal of SO.sub.2 was seen, almost doubling the removal of SO.sub.2.
The remaining graphs demonstrate tests conducted involving passing the exit gas from the reactor tube through a scrubber containing distilled water.
Graph 10 (FIG. 12)The reaction of 9,400 ppm NO with varying mole ratios of Cl.sub.2 to NO in the presence of water vapour at 450.degree. C., followed by scrubbing with water was examined. The removal was substantially complete by a Cl.sub.2 /NO ratio of 1.3.
Graph 11 (FIG. 13)The reaction of 7,000 ppm SO.sub.2 with varying mole ratios of Cl.sub.2 to SO.sub.2, dry, at 450.degree. C. followed by scrubbing with water. The removal was substantially complete at a Cl.sub.2 /SO.sub.2 ratio of 1.0.
Graph 12 (FIG. 14)The effect of SO.sub.2 on the removal of 12,000 ppm NO at 200.degree. C. in the presence of water vapour with varying mole ratios of Cl.sub.2 to NO, followed by water scrubbing, was investigated. The data indicates that the SO.sub.2 dominates in the competition for chlorine, and that NO removal does not begin until the SO.sub.2 removal is substantially complete.
Graph 13 (FIG. 15)Complementing Graph 12, the effect of NO on the removal of 6,600 ppm SO.sub.2 at 200.degree. C. with varying mole ratios of chlorine to NO, followed by water scrubbing, was examined, with and without water vapour present in the gas stream. The presence of NO or water vapour had no effect on the SO.sub.2 removal in the scrubber.
Graph 14 (FIG. 16)The effect of NO on the removal of 6,800 ppm SO.sub.2 at 450.degree. C. with varying mole ratios of Cl.sub.2 to NO was investigated. Graph 11 (FIG. 13) shows the comparable SO.sub.2 removal without the presence of NO.
A number of spot checks were conducted at various reaction conditions to determine the effect of both SO.sub.2 and NO on the removal of the gas being analyzed. The results are shown in Table 1 below. In part 1, the gas phase reaction of 9,400 ppm NO with a large excess of chlorine was found to be insensitive to the presence of SO.sub.2 in the presence of water vapour at 400.degree. C. In part 2, with a 2:l Cl.sub.2 /NO ratio, 10,000 ppm NO in the presence of water vapour was insensitive to the presence of SO.sub.2. Parts 3 and 4 deal with the effect of NO upon the SO.sub.2 removal by less than 1:1 Cl.sub.2 /SO.sub.2 ratio at 450.degree. C. using water scrubbing. In part 3, in the presence of water vapour, a consistently repeatable enhancement of SO.sub.2 by NO was observed (the readings were made consecutively as shown.) In part 4, using dry gas, no such effect was seen.
TABLE 1
__________________________________________________________________________
Hot Gas
Hot Gas
Phase Phase
NO SO.sub.2
Reaction
Reaction
Water
NO ppm SO.sub.2 ppm
H.sub.2 O ppm
Cl.sub.2 /NO.sub.2
Cl.sub.2 /SO.sub.2
Removal
Removal
Temperature
Time Srub
__________________________________________________________________________
9,400
0 27,000
4.67 -- 44.0%
-- 400 C. 9.5 sec.
No
9,300
12,000
27,000
4.95 4.67 44.2%
-- 400 C. 9.5 No
9,500
16,000
27,000
4.53 4.67 47.4%
-- 400 C. 9.5 No
10,100
0 26,000
2.07 -- 41.0%
-- 450 C. 9.5 No
10,000
16,600
26,000
2.07 1.25 41.2%
-- 450 C. 9.4 No
12,200
6,900
32,000
0.37 0.66 -- 79.4%
450 C. 9.0 Yes
0 7,000
32,000
-- 0.66 -- 65.4%
450 C. 9.1 Yes
12,600
6,600
32,000
0.35 0.66 -- 80.7%
450 C. 8.6 Yes
0 6,600
32,000
-- 0.66 -- 66.3%
450 C. 8.6 Yes
0 7,000
0 -- 0.84 -- 67.6%
450 C. 9.0 Yes
12,500
6,900
0 0.48 0.84 -- 68.1%
450 C. 9.0 Yes
__________________________________________________________________________
GENERAL PROCESS PARAMETERS BASED ON EXPERIMENTAL DATA
While the inventors do not wish to be bound by any theories, it seems possible for the purpose of assisting a person skilled in the art to understand the invention and on the basis of the graphical and tabular data to define a number of characteristics and parameters for the process:
1. In the gas phase, that is, above about 100.degree. C., but less than 650.degree. C., the reaction of NO and Cl.sub.2 appears to be enhanced by the presence of water vapour.
2. The presence of SO.sub.2 does not appear to affect the NO/Cl.sub.2 water vapour gas reaction.
3. There appears to be a water vapour enhanced gas reaction between SO.sub.2 and Cl.sub.2. NO appears to further enhance this reaction.
4. Scrubbing the effluent gas from the reactor at 200.degree. C. to 450.degree. C. with water seems to result in NO removals of 98 percent at Cl.sub.2 levels as low as 1.3 Cl.sub.2 /NO molar ratio.
5. Scrubbing the effluent gas from the reactor at 200.degree. C. to 450.degree. C. with water appears to result in SO.sub.2 removals of 99 percent at Cl.sub.2 levels as low as 1.0 Cl.sub.2 /SO.sub.2 molar ratio.
6. When NO and SO.sub.2 pass from the gas phase to the scrubber, it appears the SO.sub.2 is preferentially removed. There seems to be little effect on the remaining NO until most of the SO.sub.2 is removed. SO.sub.2 appears to dominate the absorption reaction into solution at a gas temperature of 400.degree. C.
DESCRIPTION OF ONE PROCESS EMBODIMENTA typical contemplated flue gas treatment and scrubbing facility is illustrated in FIG. 2. It will be appreciated that a number of the treatment steps may be omitted. In its simplest form, the process could simply involve treatment of the flue gas with chlorine. Recovery rates could be enhanced by following the flue gas treatment with a water scrub.
LEGEND OF FIG. 21. Firebox
2. Stack
3. Addition of chlorine, followed by hot section (9)
4. Quench
5. Venturi and associated cyclone and fan
6. Crossflow gas absorber
7. Crossflow chlorine absorber
8. CaCO.sub.3 tower
9. Chemically inert pipe
10. Stack reheat
11. Flue dust settling and filtration
12. Sludge washer
13. Collection and silt settling tank
14. Acid mixing
15. CaSO.sub.4 settling and filtration
16. Chlorine gas removal
17. Chlorine gas removal
18. Demisting
19. CaCO.sub.3 addition chute
20. Acid holding tank
A. Water means
B. Chlorine reclaim scrubber (7) effluent
C. Venturi cyclone (5) effluent
D. Filtered venturi (5) effluent
E. Sludge wash (12) solution
F. Chlorine reclaim scrubber (7) effluent
G. Dechlorinated D and F
H. Dechlorinated B
J. Acidified and filtered CaCO.sub.3 column (8) effluent
K. Acid byproduct (2) output
In the following description of the process, seven stages are described.
1. Chlorine injection and hot gas reactions;
2. Water solution quench (optional);
3. High energy scrubber for particle removal (optional);
4. Gas absorption scrubber for pollutant removal;
5. Chlorine recovery (optional);
6. Chlorine and acid vapour removal; and
7. Demister (optional).
The optional stages are included to illustrate a likely commercial application. Stages 2 and 3, for example, perform site specific functions concerning cooling the gas and particle removal which are not the subject of this invention. From a chemical viewpoint, these stages will also function in like manner as stage 4. The stages strictly relevant to the invention are 1, 4 and 6.
The first stage of the process consists of a section of chemcially inert pipe (9) or similar device, with or without baffles, preferably a baffled glass lined pipe of hold time 5 to 10 seconds. Chlorine is added in one or more of the following ways:
1. Gaseous chlorine;
2. Liquid chlorine;
3. A mixture of chlorine gas and air, inert gas or flue gas, which may also contain hydrochloric and/or nitric acid vapours.
4. A water solution of chlorine;
5. Recycled process solution containing chlorine and which may also contain hydrochloric and/or nitric acid.
The chlorine added to the gas stream is for the gaseous oxidation of objectionable components to form compounds more readily absorbed in the following scrubbers. The water vapour concentration may also be adjusted at this time by the addition of one or more of:
1. Liquid water;
2. A water solution of chlorine;
3. Recycled process solution containing chlorine, and which may also contain hydrochloric and/or nitric acid;
although the addition of the water solution of 2 or 3 may not necessarily be for the control of water vapour concentration since these solutions may be used rather for the chlorine addition with no concern for other parameters.
The chlorine being added into this section may come from one of three sources. The chlorine added as a gas, liquid or as a water solution is form the chlorine cylinder used as the process chlorine source, and one or more of these is preferred. The chlorine mixed with air, inert gas or flue gas derives preferably from using gas or warm gas to recover chlorine from the process scrubber effluent solutions by blowing. The recycled process solution containing chlorine is the effluent solution of the fifth stage of the process, the chlorine reclaiming scrubber (7). The chlorine sources other than the cylinder are intended for the return of chlorine to the earliest stage of the process for reuse of unreacted chlorine.
At this stage of the process the gas stream is 100.degree. C. or higher in temperature.
In this stage, the gas stream/chlorine mixture is left to react for a time not less than that needed to result in a 10 percent increase in absorption of an objectionable component over that which would be absorbed with this section omitted, or less than 10 percent if this is economically useful. In the case of flue gas cleanup, the component of interest is nitric oxide, NO, principally, which due to its low water solubility is difficult to remove from gases in wet scrubbers. Sulfur dioxide is sufficiently soluble that this stage is unnecessary for adequate absorption of SO.sub.2.
The SO.sub.2 and H.sub.2 S are simultaneously removed into solution in the second, third and fourth stages. Nitrogen oxides are removed from the gas stream in all of the scrubbers, but principally in the second, third and fourth stages.
The second stage of the process is an optional water quench (4), of standard design, for cooling the flue gas before entering the wet scrubber stages, if desired. Water or recycled process solution is added as a spray, with the recycled process solution again coming from the chlorine reclaiming scrubber (7) as in the first stage. Preferably, this stage is omitted unless a high temperature flue gas is being cleaned. The water solution is preferably recirculated in order to obtain as high a concentration of acid as possible in the solution although the invention is functional at a pH of less than or equal to 7.
The third stage of the process is an optional high energy scrubber (5) of standard design, which may be used when particulate removal is desired and no electrostatic precipitator is used. This scrubber is ideally a high pressure venturi or venturi with applied high intensity ionization. Preferably, electrostatic precipitation is used prior to the use of the process described here, as particulate collection is not a subject of the invention. The scrubbing solution in this stage derives from the same sources, is recirculated similarly to and for disposal may be dechlorinated in the same fashion as that in the second stage of the process. If desirable, the scrubber may be combined with the solution of the second stage in operation and disposal.
The fourth stage of the process involves a gas absorbing scrubber of standard design (6), preferably a packed scrubber such as a crossflow scrubber, but almost any scrubber of standard design may be used, with the suitability being principally determined by the gas contact time with the scrubbing solution. The scrubbing solution in this stage derives from the same sources, is recirculated similarly to and for disposal may be dechlorinated in the same fashion as that in the second stage of the system. If desirable, the scrubber solution may be combined with the solution of the second and third stage in operation and disposal.
The function of this stage of the process is the absorption of the objectionable components into solution, followed by the rapid, irreversible oxidation of these components to form either non-volatile compounds, such as sulfuric acid, or else highly soluble volatile compounds such as nitric acid which are readily contained.
The size and type of this scrubber is determined by the demands of each situation, and an installation having to deal primarily with SO.sub.2, as an example, will only need a relatively simple scrubber due to the relatively high solubility of SO.sub.2, whereas an installation handling a large amount of NO.sub.x will need a longer residence time scrubber with high liquid contact due to the lower solubility of nitrogen oxides.
The fifth stage of the process, which may be omitted or abbreviated if economy in the use of reagents is not a major consideration, or if a chlorine to SO.sub.2 molar ratio of less than 1.0 is used, is a gas absorbing scrubber of standard design (7), preferably a countercurrent packed scrubber. The size and type of scrubber used in this stage is determined by the amount of chlorine collection desired in this scrubber. The solution in this scrubber derives from the water mains. The solution may be recirculated after dechlorination by using air, inert gas, or flue gas to blow the chlorine out of solution for return of chlorine to the first stage.
The purpose of this absorber is to recover chlorine and acid vapours from the gas exiting the previous absorber, for return of the chlorine to earlier stages of the process. The effluent solution of this scrubber may be used as some or all of the feedwater in stages one through four. Due to the presence of dissolved chlorine in the scrubber, the scrubber will also continue the removal of NO.sub.x from the gas stream.
The sixth stage of the process is a packed countercurrent scrubber (8) for the removal of chlorine from the gas stream and for the return of the chlorine to previous stages of the system. The scrubber is used with a recirculating solution of a soluble carbonate, or bicarbonate, or else a soluble hydroxide such as sodium hydroxide or calcium hydroxide from slaked lime. A scrubbing solution or slurry of an alkaline earth carbonate may be used also. Alternatively, a solid carbonate such as limestone or dolomite may be used as the solid packing in the scrubber. Preferably a 50 percent solution of sodium hydroxide is used.
This stage of the process is not unlike the teaching of Howard et al., U.S. Pat. No. 3,357,796. This stage differs from Howard's teaching in that another function is present simultaneously. The absorption of chlorine into the recirculating scrubber solution results in the presence of dissolved HOCl and/or hypochlorite. This renders the scrubber solution strongly oxidizing and thus the scrubber simulataneously removes pollutants from the gas stream as well as chlorine. The scrubber is thus a device for removing both chlorine and pollutants, principally NO.sub.x, as the remaining pollutants will be normally removed to high efficiency prior to this stage.
The chlorine reacts in the sixth stage with the carbonate, bicarbonate or hydroxide to produce either a hypochlorite or hypochlorous acid, HOCl. Upon mixing with the effluent solutions from previous scrubbers (14), which are high in acidity, containing hydrochloric acid and sulfuric acid, any hypochlorite is converted to HOCl, and in the presence of HCl, the chlorine dissolution and disproportionation equilibrium results in the regeneration of free chlorine, which is blown out of the solution, preferably with flue gas (16).
If the solution from this section of the process contains calcium ions, from a CaCO.sub.3, dolomite, slaked lime or slaked calcined dolomite scrubber, steps must be taken to filter out the CaSO.sub.4 precipitated during the acidification with the HCl and H.sub.2 SO.sub.4 mixture (15).
If the solution from this sixth stage of the process contains any appreciable amount of dissolved hydroxide, carbonate or bicarbonate, the mixing with previous stage solutions must be carried out cautiously, due to the release of heat or CO.sub.2, which poses no serious problems if taken into consideration. The evolved CO.sub.2, if any, is vented into the process no later than the input of stage six and preferably earlier, since the evolution of CO.sub.2 will tend to carry acid vapours and dissolved chlorine out of the mixture.
The acidified effluent of this stage of the process may be dechlorinated as in stage five and the mixture of chlorine and air, inert gas or flue gas added to the first section of the process.
The seventh and final stage of the process consists of an optional demisting stage of standard design (18). A packed bed demister is preferred, but any demister of adequate efficiency may be used. This stage may be combined with the previous stage by making a packed scrubber and introducing the scrubbing liquid at a point below the top surface of the packing, and using the packing above the liquid introduction level as a demister.
The effluent gas from the system is routed to a stack for disposal (2) and may be reheated (10) if desired.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Claims
1. A process for oxidizing gaseous pollutants in a flue gas stream consisting essentially of flue gases, water vapor and one or more gaseous pollutants selected from the group consisting of SO.sub.2, NO, NO.sub.2, NO.sub.x and H.sub.2 S, said oxidized form of the pollutants being more readily removable from the flue gas stream by water absorption than the non-oxidized form thereof, comprising injecting sufficient chlorine in a gaseous form, a liquid form, or as a water solution thereof into the said flue gas stream while the flue gas stream is at a temperature greater than 100.degree. C. to react with the said pollutants and permitting the flue gas stream/chlorine mixture to react for a time sufficient to enable a significant amount of oxidation of the pollutants to occur, whereby an oxidized flue gas stream consisting essentially of flue gases, water vapor and one or more gaseous oxidized said pollutants is formed.
2. A process as defined in claim 1 wherein the temperature of the gas stream is between 100.degree. C. and 650.degree. C.
3. A process as defined in claim 1 wherein the temperature of the gas stream is between 200.degree. C. and 650.degree. C.
4. A process as defined in claim 1 wherein the temperature of the gas stream is between 400.degree. C. and 650.degree. C.
5. A process as defined in claim 1 wherein the gas stream following treatment with the chlorine is subjected to a scrubbing step with a water or water solution of pH less than or equal to 7.
6. A process as defined in claim 2 wherein the gas stream following treatment with the chlorine is subjected to a scrubbing step with a water or water solution of pH less than or equal to 7.
7. A process as defined in claim 3 wherein the gas stream following treatment with the chlorine is subjected to a scrubbing step with a water or water solution of pH less than or equal to 7.
8. A process as defined in claim 4 wherein the gas stream following treatment with the chlorine is subjected to a scrubbing step with a water or water solution of pH less than or equal to 7.
9. A process as defined in claim 1 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 0.5 and about 5.0.
10. A process as defined in claim 1 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 0.5 and about 5.0.
11. A process as defined in claim 2 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 0.5 and about 5.0.
12. A process as defined in claim 2 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 0.5 and about 5.0.
13. A process as defined in claim 1 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 1.0 and about 2.0.
14. A process as defined in claim 1 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 1.0 and about 2.0.
15. A process as defined in claim 2 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 1.0 and about 2.0.
16. A process as defined in claim 2 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 1.0 and about 2.0.
17. A process as defined in claim 5 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 1.0 and about 2.0.
18. A process as defined in claim 5 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 1.0 and about 2.0.
19. A process as defined in claim 6 wherein the pollutant is SO.sub.2 and the Cl.sub.2 /SO.sub.2 molar ratio is between about 1.0 and about 2.0.
20. A process as defined in claim 6 wherein the pollutant is NO and the Cl.sub.2 /NO molar ratio is between about 1.0 and about 2.0.
21. A process as defined in claim 2 wherein the gas stream following water scrubbing is subjected to a chlorine removal process.
22. A process as defined in claim 5 wherein the gas stream following water scrubbing is subjected to a chlorine removal process.
23. A process as defined in claim 6 wherein the gas stream following water scrubbing is subjected to a chlorine removal process.
| 3803290 | April 1974 | Gooch |
Type: Grant
Filed: Oct 18, 1985
Date of Patent: Oct 28, 1986
Assignee: ISCA Management Limited (Vancouver)
Inventors: Brian W. McIntyre (Vancouver), John W. Biggar (Burnaby)
Primary Examiner: John Doll
Assistant Examiner: Wayne A. Langel
Law Firm: Murray and Whisenhunt
Application Number: 6/788,835
International Classification: C01B 1700;
